Apparatus for making bifocal lenses.



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lj APPARATUS FOR MAKING lrocAL LENsEs. F-"W f I.l I

APPLICATION FILED FEB. 26. 1913.

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i i I I I I I I I if@ ,f `1 IS a Patented oet. 26, 1915.

. H. NEWB-OLD.

A A APPARATUS FOR MAKING BIFUCAL LENSESI APPLICATION FILED FEB. 26.I9I3. 1,158,002. Patented Oct. 26, 1915.

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H. NEWBOLD. i APPARATUS FOR MAKING BIFOCAL LENSESQ APPLICATION FILED-EBfZG. 1913.

Pafend om. 26, 1915.

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H. NEWBOLD. APPARATUS Fon MAKING BlFocAL LENSES. APPLICATION FILED 'FAEB26. 19|3. 1,158,002. Patented Oct. 2b', 1915.

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H. NEWBOLD.

APPARATUS FOR MAKING BIFOCAL LENSES.

APPLICATION FILED FEB. 26. I9I3,

Patented Oct. 26, 1915.

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H. NEWBOLD.

APPARATUS FOR MAKING BIFOCAL LENSES.

APPLICATION FILED IEB. 26. 1913.

Patented Oct. 26, 1915.

7 SHEETS-SHEET 64 lge/Mw? H. NEWBOLD.

APPARATUS FOR MAKING BIFocAL LEIIsEs.

APPLICATION FILEDJFB. 26. I9I3.

` Patented Oct. 26, 1915.

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Uivrinn sra'rns PATENT onnion.

HARRY NEWBOLD, 0F ST. ALBANS, ENGLAND, ASSIGNOR 0F ONE-HALF TO WARNERREED WILLIAMS, 0F LONDON, ENGLAND.

Specification of Letters Patent.

Patented O ct. 26, 1915.

Application led February 26,v 1913. Serial No. 750,841.

To all whom 'it may concern.'

Be it known that I, HARRY NEwBoLD, a subject of the King of GreatBritain, residing at Holywelh Holywell Hill, St. Albans, Hertfordshire,England, have invented new and useful Improvements in Apparatusforli/faking Bifocal Lenses, -of which the following is a specification.

This invention relates to bi-focal lenses and to apparatus for themanufacture of the same.

As is well known bi-focal. lenses as used for eye-glasses and spectacleshave been formed from a solid piece of glass, the dividing line betweenthe two curves or foci being circular or semicircular which gives risetocertain limitations in practice, since the eld of the lower focus mustbe somewhat restricted, or the dividing line must be brought into tooclose proximity to the center of the lens.

Now, my invention has for its obj ect to provide amachine for grindingbi-focal lenses in which the lower field is of oval, elliptical, orfiattened .oval or elliptical or like shape, that is to say, the lengthof which is greater inthe transverse direction than in the verticaldirection so that a wider field is provided for the lower focus withoutthe latter approaching unduly toward the center of the lens.

My improved machine comprises a rotating tool which may be of anysuitable construction, and a lens-holder, the said holder being mountedso that it can tilt in any direction upon the table which is adapted toreciprocate, or is mounted upon a second table in which it isreciprocated, the said second table being itself designed to bereciprocated upon a rigid platform or the like in a direction at rightangles to that in which the first table reciprocates, so that anelliptical or like path is given to the lensholder. The lens-holder hasfitted to its underside what I term a former whichis of a plano-convexor plano-concave shape and is supported upon a similarly dimensionedplano-concave or plano-convex former secured upon the rigid platform,the two formers lying one upon, or within, the other and the contactingsurfaces being preferably smeared with oil so as to insure a goodsuction contact and a frictionless motion of the surfaces one over theother. The two tables are actuated by eccentrics, cranks or the likepend upon the eccentric or other driving' gear. Vihere one table only isemployed, then obviously the lens is merely reciprocated to and fro inone direction only.

The grinding tool is-mounted above the lens holder and is brought tobear on the top of the glass to be ground, the said tool being rotatedand the lens-holder reciprocated at the same time. As the holderreciprocates the lens being ground follows the contour of the formers,and since the tool rotates on a rigid upright aXis, the glass isgradually ground until it eventually reproduces the shape of thecontacting surface of the two formers. It will be obvious that inpractice allowance iS made to correct the error which would otherwisearise owingv to the distance between the surface of the formers and theglass being ground.

In an alternative form of machine the lens to be operated upon is firmlyfixed upon a rigid table or platform, the grinding tool being caused tomove in the desired oval path upon the machine. The concavity isobtained from the grinding tool which is mounted through the medium ofaball and socket 'or universal attachment upon an upright standard, thesaid tool being guided, so as to conform to the movement of the table byan attachment carried by the latter. The ball and socket fittingconstituting the pivot or former around which the tool spindleoscillates, can be adjusted in the vertical position upon the standardso as to regulate, as desired, the radius of curvature obtained therebyon the lens.

To enable the invention to be fully `understood, l will describe it byreference to the 'accompanying drawings, in which Figure l is a view ofone form of bi-focal lens groundY according to the invention. Figs. 2and 3 are a sectional front view and a sectional side view of a machinefor grinding a lens as shown in Fig. l. Fig. 4 iS a sectional plan viewof the machine. Fig. 5 is a view illustrating the method of operationthereof. Fig. G is a sectional front view illustrating a modied form ofma- Q lOO ' A faces vone over the other.

chine. Fig. 7 is a sectional Side view thereof,

and Fig. 8 a sectional plan of the machine,

5 of the machine. Fig. l0 is a sectional side view thereof. Fig. 1l is asectional plan view.

w v'Referring first to the construction of machine illustrated in Figs.2 to 5, a represents the frame of the machine and b 1s thelinrlthebearing's h1 securedto the upper part of the frame a and isadapted to be driven by the pulley c in the lrnown manner. This grindingtool is preferably of mild steel which is turned to the desired curveand case-hardened or it may be of brass or gunmetal sheathed with steeland case-hardened.

d is the lens-holder to the upper face of which the lens e to be groundis cemented in the usual way, the said lens-holder being rectangular inshape and being provided with a pin f projecting from each'side whichpins engage in notched lugs g upon the table 25 z which is designed tobe reciprocated upon the table i itself arranged to reciprocate on therigid platform j projecting from the machine frame a, the said table ireciprocating in a direction at right angles to that in which the tableL moves.

c is the upright driving spindle which is mounted in the bearing klsecured to the frame a below the platform y', and Z, Z1 are the twocranks upon the driving shaft c which respectively serve to reciprocatethe lens-holder or table 7L and the table z'.

fm, is the former V`which in the arrangement illiistifatedforms partofthe lenshol der al `aiidnwhich is of a plano-concaveV shape and theplano-convex former secured upon `the rigid platform y', the former mresting Kupon the former m1, and the contacting surfaces being smearedwith oil as above de- Nscribed so as to insure a good suction contactand a frictionless motion of the surbe brought sothat it bears on thetop of the"u said lens, the said tool is then rotated and the drivingspindle le also rotated so that the tables l1, and 'i reciprocate uponthe fixed 56 platform j, that is to say, relatively to Athe tool b whichrotates on a rigid upright axis. As the two tables reciprocate in themanner stated the lens c being groundis caused to follow the contour ofYth`egtwo formersjlt, m1

60 and as the tool rotates on a Arigid upright axis the lens isgradually" ground until Afinally there is reproduced upon it the shapeof the contacting surfaces of the said two dforlners, As above"described allowance in G5 practice is made in order to correct theerror rotating grinding t'lwwhich is mounted which would otherwise occurarising from the distance between the surface of the former and that ofthe lens being ground.

In Figs. 6, 7 and 8, which representa /g multiple machine that is tosay, a machine in which two (or more) lenses can be simultaneouslyground, the lens-holder d is formed on its underside as before with theformer surface m which contacts with the former m1, the two formersurfaces being held in contact by means of the fork n the two legs ofwhich bear upon pins nl projecting from the side of the lens-holder d.This fork has a stem o which is pivotally mounted in the sleeve 01 alsopivotally mounted at right angles to its own axis in the bracket o2fixed to the table p so as to form a universaljoint, a spring 03 beingprovided for normally causing the fork to be pressed downward so as tohold the two former surfaces in contact. The table p is reciprocated soas to execute the elliptical or other motion desired through the mediumof the two cams p1 and p2 which are mounted upon the upright spindle p3and respec-A tivelyengage the superposed slots p0 and p4' provided inthe said table. The combined motions given by the two cams as thespindle rotates result in the particular elliptical or like curvedesired. The other end of the table p is provided with a slot p5 withwhich engages a cam p corresponding to the cam p2 and mounted upon anupright spindle p7, both the spindles 723 and p7 being driven by bevelgearing g from a driving shaft g1 mounted beneath the platform j of themachine. The tool b in this case is rigidly mounted as described withreference to the machine illustrated in Figs. 1 to 4 and the operationof the machine is similar to that above described.

Figs. 9, 10 and l1 illustrate a modified machine in which the radial.motion necessary for obtaining the curvature of the lens and theelliptical shape of the latter is obtained by imparting a swingingmovement to the grinding tool. This is effected as follows The lens c tobe ground is cemented in the usual way to the lens-holder cl which isfixed upon the platform j of the machine frame The grinding tool Z) issuspended from a universal joint, comprising a ball or;

sphere r through a pulley on which the said tool can freely slide andwhich is movably held in a bearing .s' adjustably mounted upon astandard s1 erected on the machine frame a. The ball 1 is movable. inany direction in its spherical bearing s so that the spindle I) has afree movement from this point of suspension, the said spindle beingrotated by means of a pulley t which rotates upon a sleeve r1 extendingfrom the ball or sphere 7' and has a pin t1 designed to engage with apin t2 projecting from the cutting tool b so that as the said pulley trotates the pin t1 makes contact with pin t2 and correspondingly rotatesthe cutting tool.

mounted in the forked spherical bearing 'w1 which is adjustably carriedby an upright u2 upon the carriage p. The carriage p is given ellipticalmotion upon the platform j by mechanism similar to the means whichoperate the carriage p shown in Figs. 6, 7 and 8. With this constructionof machine it will be obvious that as the carriage p is reciprocated andthe cutting tool b at the' same time rotated, the said tool is caused tooscillate about its pivot 7' and at the same time is given theelliptical motion desired so that the concave elliptical surface isground upon the lens.

Fig. l shows one form of lens produced according to my invention. Itwill be obvious, however, that the shape of the lower field may bevaried in a number of ways vand in fact it may be of any curved shapeother than circular or semi-circular, which are the only shapes whichcan be produced by machines at present in vogue. Furthermore, lensesmade according to my invention possess several advantages in practice.In the first place, the position of the optical center of the lower ormore positive field can be absolutely controlled, secondly, the iield ofvision of the lower or more positive field is extended, and the upperfield of which, in ordinary working, the optical center is undercontrol, is at the same time of larger field relatively to that of thepositive field than has hitherto been possible. Also the more positivefield can be inserted between two portions of the more negative field,thus rendering the lens particularly convenient to the wearer whendescending stairs, for eX- ample.

I claim- 1. A machine for grinding bi-focal lenses comprising means forholding the lens, a rotatable grinding tool for grinding the same,

and means for imparting to one of said parts rocking and ellipticalmovement, whereby an'elliptical concavity is formed in the lens.

2. A machine for grinding bi-focal lenses comprising a lens holder, arotatable grinding tool, and means for imparting to said grinding tool,rocking-and elliptical move- The lower end of the cutting tool passesthrough a second swivel joint comprising the ball up' comprising astationary lens holder, a rotatable grin ing tool suspended by auniversal joint so that it can oscillate around the same,

and means for imparting substantially'elliptical motion to said tool.

4. A machine for grinding bi-focal lenses comprising a lens holder, arotatable grinding tool, a universal joint in which the upper end of thegrinding tool is rotatably mounted, and means provided near the lowerend of said grinding tool for moving the lower end of said toolsubstantially elliptically.

5. A machine for grinding lenses comprising a frame, a universal jointadjustable 7. A machine for grinding lenses comprising an upperuniversal fitting, a grinding tool having its upper end rotatablymounted in said fitting, a lower universal fitting in which the lowerend of said grinding tool is rotatably mounted, adjustable carryingmeans for said lower universal fitting, and means for moving saidadjustabllle carrying means substantially elliptica y.

8. A machine for grinding lenses comprising an upper universal fitting,a grinding tool having its upper end rotatably mounted in said fitting,a lower universal fitting in which the lower end of said grinding toolis rotatably mounted, carrying means for said lower universal fitting, acarriage 'upon which the carrying means is rigidly mounted, saidcarriage being provided with an upper and lower slot at right angles toone another, and a plurality of eccentrically mounted rotating disksadapted to travel in said slots to move saidgkcar-- riage in asubstantially elliptical path.

HARRY NEWBOLD.

ment, whereby an elliptical concavity is-'f'flVitnesses:

formed in the lens.

3. A machine for grinding bi-focal lenses JOHN E. BoUsrInLn C. G.REDFEN.

